G. F. Jacky described the electroplating of copper-tin-zinc alloy in September 1971 in Plating and Surface Finishing at 883-887. A practical implementation of the Jacky bath included:
Cu.sup.+ : 0.40-0.48 oz/gal PA1 Zn.sup.+2 : 0.18-0.22 oz/gal PA1 Sn.sup.+4 : 0.15-0.20 oz/gal PA1 NaCN: 2.7-3.1 oz/gal PA1 Na.sub.2 CO.sub.3 : 4.0-10 oz/gal,
had a pH of between 12.3-12.7, and was used for electrodeposition of a bright ternary alloy with a composition generally in the range of 50-60 wt % copper, 20-30 wt % tin, 15-25 wt % zinc, when plated at current densities of 5-45 ASF and temperatures of 120.degree.-180.degree. F. without the addition of the organic brightener. A small amount of 50% H.sub.2 O.sub.2 was added to the bath to oxidize the tin to the +4 (stannic) valence state.
Products plated with the Jacky bath or its close equivalent were found to encounter severe tarnishing problems as they underwent a cleaning step prior to soldering. The plated parts turned brown if the plate had less than about 10.9 atomic wt % tin (about 18.7 wt %). Parts found to have a higher atomic wt % tin when analyzed with Auger spectroscopy remained untarnished. Parts with a slight discoloration had a tin content close to the 10.9 atomic wt % tin. To ensure desired corrosion resistance and to achieve desired aesthetic qualities of the plated parts, it was important to find a method for plating which would ensure that the copper-tin-zinc alloy would have at least 10.9 atomic wt % tin when plated. In this regard, the Jacky bath was unsatisfactory, in that it could not be controlled to obtain plated products having the targeted copper-tin-zinc alloy content.